In motor vehicles having a so-called common rail injection system (also referred to as accumulator injection system), a plurality of, typically all, injectors are coupled to a common fuel distributor (common rail) which is under a high pressure. The amount of fuel to be injected into the cylinders of the internal combustion engine in each case within a cylinder cycle, also referred to as operating cycle, is typically primarily metered by virtue of the fact that the respective injector is actuated with an actuating period, which is selected to be shorter or longer, in order to inject fuel into the respective cylinder. The injector is in each case opened during the actuating period.
By virtue of manufacturing tolerances and aging phenomena in the injection system, the injection masses can vary between the individual cylinders. This can lead to torque differences between the cylinders, which can have a negative effect on the running smoothness or the emission behavior of the internal combustion engine. Thus, particularly wear phenomena or deposits can lead to a situation in which an actual opening period or an actual degree of opening of the injector for a given fuel pressure and a given actuating period is changed during a service life of the injectors.